1. Field of the technique
The present invention relates to a brush holder which is applied to a small size electric motor or other devices.
2. Prior art
One example of a prior art brush holder of a small size is disclosed in Japanese Utility Model Publication No. 56-31166. FIG. 1 is a disassembled perspective view of the brush holder shown in the Publication, and FIG. 2 is a sectional view illustrating a main part of the brush holder of FIG. 1 after it is assembled. In the figure, reference numeral 101 denotes a brush box, numerals 101a and 101b denote slits formed at opposite sides of the brush box 101 and numeral 103 denotes a top plate including bent pieces 103c and 103d opposing to each other which are to be inserted into the brush box 101, the bent pieces 103c and 103d being provided with nails 103a and 103b capable of engaging with the slits 101a and 101b. Numeral 107 denotes a solder portion connecting a pigtail 104 and the top plate 103. Numerals 102 and 105 denote a brush and a brush spring, respectively.
With the structure as above, the top plate 103 is fixed to the brush box 101 by engaging the nails 103a and 103b of the top plate 3 with the slits 101a and 101b of the brush box 101.
In the prior art brush holder, a brush terminal 103 (top plate) formed by bending is directly inserted for fixation thereof within the interior of the brush box 101 constituting a sliding surface for the brush 102, so that the upper end of the brush spring 105 locates at the position lower than the upper end of the brush box 101. Therefore, the brush box must cover this additional length beside that for the brush 102, which results in a longer brush holder. It is a problem for miniaturization of an electric motor.
Further, in the prior art brush holder, the longer the height of the bent pieces 103c and 103d of the brush terminal 103, the easier the bending operation of the opposing side portions and the insertion of the brush terminal 103 into the brush box 101 become. However, this seriously leads to the above problem that the length of the brush box becomes larger. Thus, it is necessary to shorten the length of the height. However, a larger force is required to bend the opposing sides or the nails 103a and 103b. It becomes difficult to insert the brush terminal 103 into the brush box 101.